ADELAIDE, AUSTRALIA—People migrated from modern-day Turkey and the Near East to colonize Europe during the agricultural revolution of the Mesolithic period some 7,500 years ago, according to a new study of mitochondrial DNA taken from skeletal remains discovered in Germany and Italy. But their population was later replaced by another group. “What is intriguing is that the genetic markers of this first pan-European culture, which was clearly very successful, were then suddenly replaced around 4,500 years ago, and we don’t know why,” said Alan Cooper of the Australian Center for Ancient DNA.